Method of making molds or cores utilizing a backup cover



Oct. 18, 1955 K. D. SHAW METHOD OF MAKING MOLDS OR CORES UTILIZING A BACKUP COVER Filed March 1, 1952 INVENTOR. Kev/wryfl. fmW

lrmle v United States Patent Office 2,720,687 Patented Oct. 18, 1955 NIETHOD OF MAKIN G MOLDS OR CORES UTILIZING A BACKUP COVER Kenneth D. Shaw, Vineland, N. 5., assignor of twentythree and one-third per cent to M. Joseph Greenbiatt, Vineland, N. J.

Application March 1, 1952, Serial No. 274,368 6 Claims. (Cl. 22-193) The present invention is directed to molds, and more particularly to a method of making molds or cores adapted particularly for use in the casting of metals.

It has been customary to produce molds from sand by the use of a pattern around which the sand was tamped to form a relatively dense body which could be handled. Such sand molds were assembled in a suitable flask and molten metal poured into the same. When the metal solidified, the flask was opened, the sand mold destroyed and the casting removed. Such methods have been in use for many years and a number of difiiculties have been noted in the use thereof. In making the sand mold it often happened that the tamping was insutlicient to accurately contact the surface of the pattern. Also in removing the pattern from the sand mold, damage thereof was likely to occur, making much hand labor necessary to repair the sand mold. Similarly in assembling the sand molds and in the casting of the metal, damage often occurred so that as a result, many castings were so imperfect as to make it necessary to discard them. Where such castings had relatively minor defects, considerable labor was required in order to correct such defects.

The present invention is intended and adapted to overcome the difficulties and disadvantages inherent in prior methods, it being among the objects of the present invention to provide a method of making molds and cores from sand or the like which is adapted to produce a strong mold which may be handled in the normal manner without danger of damage thereof or destruction thereof.

it is also among the objects of the present invention to provide a method of the type described, wherein the molds or cores formed may be utilized in conjunction with casting machines whereby a high degree of production is obtainable.

In practicing the present invention there is provided a pattern as usual, which may be of wood, metal or the like. There is provided a backup mold which is placed over the pattern, with a relatively narrow space therebetween, said space being substantially uniform in depth and conforming with the shape of the pattern. There is also provided a bonding agent which may be a thermoplastic but preferably a thermosetting synthetic resin. Said agent is incorporated in a sand mixture, the

amount of agent being small relative to the amount of sand. By suitable means the mixture is injected into the space between the pattern and the backup mold, suitable vents being formed in the backup mold to insure that the space will be completely filled. The assembly is then placed in a suitable oven or otherwise heated to cause setting of the resin and forming of a strong sand mold which can be readily handled.

In the accompanying drawing constituting a part hereof and in which like reference characters indicate like parts,

Fig. 1 is a top plan view of a backup mold and pattern made in accordance with the present invention;

Fig. 2 is a side elevational view thereof and Fig. 3 is a vertical cross-sectional view taken along line 33 of Fig. l and showing in addition the backup cover and fragmentary portions of a sand blowing machine.

There is provided a pattern consisting of a facing plate 1 of wood or the like, having the pattern 2 thereon. The pattern is in this case one-half of a wheel having a central hub, a web, and a rib 3. A pair of holes 4 is provided at opposite ends thereof. A backup cover usually made of metal consists of a hub portion 5 and end portion 6 and conforming in shape to the surface of pattern 2. Openings 7 in opposite ends thereof are intended to aline with openings 4. An extension 8 on one side of the backup mold has one or more openings 9 constituting gates for the entrance of molten metal.

A space 10 is formed between pattern 2 and backup mold 56, said space being relatively narrow but a sntficient depth so that a strong body of sand results from the operation. A central opening 11 in portion 5 of the backup mold provides an entrance for sand into space 10. A series of openings 12 and 13 act as vents to allowthe escape of air and to avoid forming blow holes or other defects in the sand mold.

Depending pins 14 are attached to a suitable base such as the ordinary sand blowing machine 15. A backup cover 16 has an inner configuration 17 like the outer configuration of the backup mold so as to fit fairly tightly thereon, leaving but a very narrow space therebetween. An opening 18 is adapted to be alined with opening 11. Washer 19 is intended to provide a pressure-tight seal between the backup mold and backup cover. A similar washer 26 forms an air-tight seal between the backup cover and the sand blowing machine which has an opening 21 in alinement with opening 18. If desired, a ring washer 22 may be provided so as to contact with a corresponding portion of the sand blowing machine in order to properly aline the several elements.

In the operation of the method, backup mold 5-6 is placed on pattern 23 with openings 4 and 7 in alignment. Backup cover 16 is attached to sand blowing machine 15, sprayed with a parting agent so as to insure that the sand will not adhere thereto. The assembly is placed on a table and by any suitable means such as an air clam it is raised up into position against backup cover 16. Pins 14 enter openings 7 and 4 and insure the proper alinement of the elements. When washer 19 is in contact with hub 5, the blowing machine is operated, forcing a mixture of sand and bonding agent into space 10. This mixture may be made of ordinary foundry sand having intimately mixed therewith from 2% to 7% of a thermosetting phenol formaldehyde resinous condensation product.

The sand mixture being blown in under a substantial pressure will completely fill space 10 and will extend through vent openings 12 and 13 and form a shallow head of sand between the backup mold and backup cover. This provides an anchor that prevents accidental displacement of the sand in space 10.

The air clamp is then released, causing the pattern and associated parts to return to the initial position. This is then introduced into an oven at a temperature of about 350 F. for a sufficient length of time to harden or set the resin. This forms a porous mass which is strong and rigid and may be handled in the normal manner without danger of breaking. The sand mass is porous and, therefore, will allow gases to escape, which would prevent the formation of blow holes and weak areas in the metal to be cast in such a mold.

The pattern is removed from the assembly, leaving the backup mold and the sand mold as a unit. In the case of the specific wheel shown in the drawing, two such combinations of backup mold and sand mold are fitted as shown in Fig. 3. The pattern is usually together and clamped. Molten metal is then caused to pass through the gates formed in the sand mold so as the details may be made within the spirit of the invention.

Forinstance, the bonding agent may be any other synthetic or natural plastic or resin capable of acting to hold the particles of sand together. The bonding agent may be mixed with the sand in the form of a powder or a solutionthereof may be sprayed thereon with suitable agitation.

. The pattern may be of as many pieces as may be necessary for the article to be cast and the sand molds formed in the present methodare assembled to form the complete mold. Cores of sand and a bonding agent may be made in the same manner as molds.

. The backup mold may have more than one opening 11 for introduction of sand mixture, depending upon the shape and size of the casting and the cover and sand blowing machine may have openings corresponding thereto. Similarly the number of vents and gates may be varied in acordance with the conditions encountered. The backup cover may be attached to the sand blowing machine or may be separate therefrom and be released together with the backup mold. The cover may have extensions on the. ends thereof with openings for pins 14 so as to aline the same with the other elements.

The pattern may have the ordinary draft and the backup mold may have backdraft for picking up the sand mold and holding'it-in position. 'If desired, the backdraft may be omitted. Any suitable parting agent may be applied to the pattern, such as a silicone resin dissolved in a thinning agent such askerosene, toluol or methyl ethyl ketone. The temperature and time for setting the bonding agent will vary greatly with the nature of the bonding agent and the size and shape of the sand mold. Instead of conductingthe setting operation in an oven, heat may a be applied directly to the backup mold. The backup mold and cover may be used either in the hot or cold condition in the operation.

I claim:

1. A method of casting metals which comprises providing a pattern, placing thereover a backup mold the inner surface of which corresponds in configuration with the outer surface of said pattern but spaced therefrom, placing over said backup mold a backup cover the inner surface of which corresponds in configuration with the outer surface of said backup mold, said backup mold and cover having alined openings, said backing cover and backing mold being in contact, blowing a mixture of sand and bonding agent through said openings and into said space, removing said mold and pattern, heating the same to set said mixture and form a mold for casting, removing said pattern from said casting mold, and casting molten metal into said casting meld.

2. A method of casting metals which comprises providing a' pattern,'placing thereover. a backup mold the inner surface of which corresponds in configuration with the outer surface of said pattern but spaced therefrom,-

placing over said backup mold a backup cover the inner surface of which corresponds in configuration with the outer surface of said backup mold, said backup mold and figuration with the outer surface of said mold, alined cover having alined openings, said backing cover and backing mold being in contact, blowing a mixture of sand and bonding agent through said openings and into said space, anchoring said mixture in said mold, removing said mold and pattern, heating the same to set said mixture and form a mold for casting, removing said pattern from said casting mold, and casting molten metal into said casting mold.

3. Apparatus for casting metals comprising a pattern, a

- backup mold thereover, the inner surface of said mold corresponding in configuration with the outer surface of said pattern, said surfaces being separated sufliciently to define an enclosed space, a backup cover over said mold, the inner surface of said cover corresponding in .con-

openings in said mold and cover, means for relatively moving said mold and cover into and out of contact, and means for blowing a mixture of said. and bonding agent through said openings when said mold and cover are in contact.

4. Apparatus according to claim 3 in which said backup.

mold has at least one vent opening adapted to anchor. said mixture to said mold.

5. Apparatus according to claim 3 in which said backup mold has backdraft for holding said mixture.

6. Apparatus according to claim 3 in which said back-- up cover and mold have means for forming a pressuretight seal there-between.

References Cited in the file of this patent UNITED STATES PATENTS Whitehead Feb. 10, 1948 OTHER REFERENCES The Foundry, Oct. 1950. Pages 162,164, 168. Article by Less. 

